The present invention relates to tools for assembling disc drives. More particularly, the resent invention relates to a semi-automated tool and process that reduces the time required to first remove and then replace a stack of discs onto a spindle motor of a disc drive.
Disc drives are used to record and reproduce information stored on recording xe2x80x9cmediaxe2x80x9d or discs. Conventional disc drives employ a plurality of vertically-arrayed discs, each disc having a top and bottom surface with a magnetic coating for storing data. The discs are spaced from one another by a distance sufficient to allow magnetic read/write heads to pass over both the top and bottom surfaces of adjacent discs.
The vertical array or xe2x80x9cstackxe2x80x9d of discs are typically journaled about the cylindrical hub of a spindle motor which is mounted on a fixed shaft for high speed rotation within the disc drive housing. The disc stack includes a bottom disc supported by a lower flange of the spindle motor hub. A series of additional discs and spacer rings are then stacked on top of the bottom disc in an alternating pattern. Once the disc stack and spindle motor have been assembled into a xe2x80x9cdisc pack,xe2x80x9d a clamp ring is fitted over both the top of the spindle motor hub and the top disc of the disc stack to secure the discs and the spacer rings to the hub. Following assembly, the disc pack is spin balanced and counterweights are applied as necessary to reduce any wobble or run-out due to imbalance or an offset center of gravity. In light of recent increases in track density on current generations of disc drives, even small degrees of disc wobble can lead to tracking errors.
Thus, each disc pack is typically required to pass a number of diagnostic and spin balancing tests before installation within a disc drive. However, if the disc pack fails any of the tests, it is typically sent for xe2x80x9creworking.xe2x80x9d For example, if a diagnostic shows that one or more of the discs are defective, the entire disc pack must be reworked to replace the defective disc. Likewise, reworking is required if the spindle motor is found to be defective or if the imbalance of the disc pack is too large to be cured by counterweights. It is common for approximately 10-15% of disc packs on a production line to require reworking.
Reworking a disc pack requires that each of the discs and the spacer rings be removed one at a time and stacked in inverse order on a rack. Even if only one of the discs is found to be defective (e.g., the second disc from the top of the stack), it is typically required that all of the discs and spacer rings be removed and then restacked on the spindle motor hub to ensure that the discs are properly centered and balanced after reworking. Indeed, a shim is typically applied to the empty motor hub prior to restacking the discs to aid in centering the discs and spacer rings about the motor hub, thereby maintaining the concentricity of the discs and reducing run-out errors. However, the process of manually transferring each disc and spacer ring from the spindle motor to a stand, and then transferring all of the discs and spacer rings back to the spindle motor requires a great deal of time and operator skill to prevent damaging the fragile discs during the reworking process. However, even with skilled operators, the manual handling of each disc within the disc pack will inevitably damage a number of discs. Furthermore, although the disc drive assembly line is located within a clean room facility, the time-consuming rework process increases the chances that the discs will be exposed to contaminants that will adversely affect the performance of the disc drive.
It is with respect to these and other background considerations, limitations and problems that the present invention has evolved.
The present invention provides apparatus and a process for reworking a disc pack having a spindle motor and a plurality of discs separated by spacer rings. Reworking of a disc pack is typically required to replace a defective disc or spindle motor or to simply restack the discs on the spindle motor to improve the concentricity or balance of the disc pack.
In accordance with a preferred embodiment of the present invention, a media rework tool includes a base and a slider plate connected to move laterally along the base. A chuck attached to the slider plate is adapted to secure the spindle motor so that the disc pack moves with the slider plate. The slider plate moves the disc pack between a retracted position (for loading and unloading the disc pack and for changing defective discs or spindle motors) and an extended position where the disc pack engages both a gripper assembly and a media guide. The media guide is substantially cylindrical in shape and extends vertically downward in alignment with the spindle motor when the slider plate is in the extended position. The gripper assembly includes a plurality of opposing arms operated in pairs to selectively grasp individual discs within the disc pack. The gripper assembly is connected to move vertically relative to the base to transfer one or more discs held by the opposing arms (together with any intermediate spacer rings) to the media guide to allow the remainder of the disc pack to be retracted with the slider plate for reworking (such as for replacement of a defective disc or motor). The gripper assembly also acts to restack the discs and the spacer rings on the spindle motor before opening the opposing arms and releasing the discs.
In accordance with a further preferred embodiment of the present invention, a method of reworking a disc pack includes centering the disc pack on a media rework tool between opposing arms of a gripper assembly and beneath a vertically-oriented, cylindrical media guide. A plurality of the opposing arms close to grasp a predetermined number of the discs, the predetermined number being one or all of the discs in the disc pack or any number in between. The gripper assembly is then raised to transfer the predetermined number of discs, and any intermediate spacer rings, from the spindle motor to the media guide. If a defective disc is being replaced, the predetermined number of discs raised by the gripper assembly will leave the defective disc exposed at the top of the remaining disc stack so that an operator may replace the defective disc. Alternatively, if the spindle motor itself is to be replaced, or if a complete restacking of the disc pack is otherwise required, then the predetermined number includes all of the discs. Once the defective disc or spindle motor has been replaced, the spindle motor is again centered under the media guide and between the opposing arms of the gripper assembly. The gripper assembly is then lowered from the media guide to restack the discs and spacer rings on the spindle motor. The opposing arms are then opened to release the discs and complete the reworking process.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.